1. Field of the Invention
The present invention relates to a separator for a fuel cell that improves power characteristics of the fuel cell, and a fuel cell comprising the same.
2. Description of the Related Art
As importance of alternative energies emerges in response to the exhaustion of energy resources, fuel cells are attracting considerable attention as a next regeneration energy source. In particular, fuel cells are actively researched owing to advantages of high efficiency and eco-friendliness.
A stack, which is an essential component of a fuel cell system, is an assembly of laminated unit cells, and each unit cell includes a membrane electrode assembly (MEA) and a separator (bipolar plate).
Separators are the most commonly used for manufacture of stacks. Depending on separator shape, structures of the stack are determined The separator performs various functions, for example, supplies hydrogen and oxygen to a cathode, prevents mixing of the supplied gas, moves electrons generated during reactions in electrodes, and discharges water generated in the cathode to the outside. Accordingly, the separator should have superior conductivity, facilitating movement of electrons, and should have surface characteristics, enabling produced water to be efficiently discharged. Also, in order to prevent mixing of gas supplied to the cathode, gas permeability is also important and other properties such as corrosion resistance and strength depending on driving environments and operation conditions of fuel cells are also required.
Developed and commonly used materials for fuel cell separators are graphite, a composite of graphite and a resin, or metals such as stainless steel or aluminum.
A voltage generated by electrode reaction in one cell manufactured using such a separator is constant, independent of a material or area of the separator, but current is proportional to a reaction area with a catalyst. Accordingly, power of a fuel cell depends on separator area. Accordingly, in order to increase power, an increase in fuel cell separator area is necessary. However, the increase in fuel cell separator area disadvantageously complicates molding and processing and causes an increase in cost due to increased manufacturing equipment area.